Molded housing friction device having stable torque over temperature range

Abstract

One aspect is an insert molded friction torque device with a rotatable shaft, a friction element mounted over the rotatable shaft in an interference fit, a rigid enclosure structure at least partially enclosing the friction elements, and a single-piece molded housing enclosing the friction element and at least partially enclosing the rigid enclosure structure such that a first portion of the housing is between the friction elements and the rigid enclosure structure within the rigid enclosure structure and a second portion of the housing is outside the rigid enclosure structure.

What is claimed is: 
     
       1. An insert molded friction torque device comprising:
 a rotatable shaft; 
 a friction element mounted over the rotatable shaft in an interference fit; 
 a rigid enclosure structure at least partially enclosing the friction elements; and 
 a single-piece molded housing enclosing the friction element and at least partially enclosing the rigid enclosure structure such that a first portion of the housing is between the friction element and the rigid enclosure structure within the rigid enclosure structure and a second portion of the housing is outside the rigid enclosure structure. 
 
     
     
       2. The insert molded friction torque device of  claim 1 , wherein the rigid enclosure structure is a solid ring that radially surrounds the friction element. 
     
     
       3. The insert molded friction torque device of  claim 1 , wherein the rigid enclosure structure is a pair of cup portions that axially enclose the friction element on either side of the friction element. 
     
     
       4. The insert molded friction torque device of  claim 1 , wherein the rigid enclosure structure is a slotted ring that radially surrounds the friction element. 
     
     
       5. The insert molded friction torque device of  claim 1 , wherein the rigid enclosure structure has an axial length along an axis of the shaft the friction element includes a plurality of clips stacked along the shaft, the plurality of clips have a length along the shaft and wherein the length of the rigid enclosure structure is greater than or equal to the length of the plurality of clips. 
     
     
       6. The insert molded friction torque device of  claim 1 , wherein a gap between an inner surface of the rigid enclosure structure and a diameter defined by the outermost surface of friction elements is less than 50% of the diameter defined by the outermost surface of the friction elements. 
     
     
       7. The insert molded friction torque device of  claim 1 , wherein a gap between an inner surface of the rigid enclosure structure and a diameter defined by the outermost surface of friction elements is less than 25% of the diameter defined by the outermost surface of the friction elements. 
     
     
       8. An insert molded friction torque device comprising:
 a rotatable shaft; 
 a friction element mounted over the rotatable shaft in an interference fit; 
 a rigid ring enclosure radially enclosing the friction elements and having at least one side opening to an inside of the ring enclosure; and 
 a single-piece molded housing enclosing the friction element and at least partially enclosing the rigid ring enclosure such that a first portion of the molded housing is inside the rigid ring enclosure and between the friction element and the rigid ring enclosure structure and a second portion of the molded housing is outside the rigid ring enclosure. 
 
     
     
       9. An insert molded friction torque device comprising:
 a rotatable shaft; 
 a friction element mounted over the rotatable shaft in an interference fit; 
 a first rigid enclosure element mounted over the shaft on a first side of the friction element and a second rigid enclosure element mounted over the shaft on a second side of the friction element opposite the first, where the first and second rigid enclosure elements each have an outer diameter that is larger than a largest outer diameter of the friction element, thereby axially enclosing the friction element in between the first and second rigid enclosure elements; and 
 a single-piece molded housing enclosing the friction element and at least partially enclosing the first and second rigid enclosure elements such that a first portion of the housing is between the friction element and first and second rigid enclosure elements within the first and second rigid enclosure elements and a second portion of the housing is outside the first and second rigid enclosure elements. 
 
     
     
       10. The insert molded friction torque device of  claim 1 , further comprising a lubricant between the friction element and the rotatable shaft. 
     
     
       11. The insert molded friction torque device of  claim 1 , wherein the friction element comprises one of a plurality of clips stacked along the shaft, a question mark band wrapped around the shaft, drag springs wrapped around the shaft, and friction discs mounted on the shaft. 
     
     
       12. The insert molded friction torque device of  claim 1 , wherein the rigid enclosure structure at least partially encloses the friction elements and also includes an opening such that the molded housing extends within the rigid enclosure structure through the opening. 
     
     
       13. The insert molded friction torque device of  claim 1 , wherein the molded housing is cylindrical body with torque transmission features. 
     
     
       14. The insert molded friction torque device of  claim 1 , wherein the molded housing is a gear. 
     
     
       15. The insert molded friction torque device of  claim 1 , wherein the molded housing is a plastic material having a coefficient of thermal expansion that is at least 2 times that of the friction element and the shaft.